Metropolitan Police officer Tom Harrison, who goes by the name “Mr. Gorilla,” raised a reported $33,650 for the Gorilla Organisation, which is dedicated to conserving gorillas in countries including Rwanda and Uganda.

The 41-year-old Londoner started the 26.2-mile route last Sunday and crossed the finish line on Saturday.

Harrison slept at friends’ houses in the evenings after completing around 10 to 12 hours and 4.5 miles per day. He has swapped between crawling on his hands and knees and up on his hands and feet to save his blistered knees.

He crossed the finish line in central London flanked by his two sons — and beating his chest.